turn overrides table structure

The Turn_Overrides table holds information on allowed turn/connection overrides to be used

Overriding the logic that creates the Connections table is done using this table in the following way:

A penalty of -1 means that this turn is prohibited A non-negative penalty means that this turn is allowed

The table is indexed on node

Table Structure

Field	Type	NULL allowed	Default Value	Foreign key	Description
turn_pen*	INTEGER	NO			ID of the override
link	INTEGER	NO		Link(link)	Movement coming from this link
dir	INTEGER	NO			link direction the movement is coming from
to_link	INTEGER	NO		Link(to_link)	Movement going to this link
to_dir	INTEGER	NO			link direction the movement is going to
node	INTEGER	NO		Node(node)	Node where the turn is happening
penalty	INTEGER	NO	-1		Penalty for the turn. -1 means the turn is blocked
notes	TEXT	YES			User notes, generally why this override was instituted

(* - Primary key)

The SQL statement for table and index creation is below.

CREATE TABLE IF NOT EXISTS Turn_Overrides(
    turn_pen  INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
    link      INTEGER NOT NULL,
    dir       INTEGER NOT NULL,
    to_link   INTEGER NOT NULL,
    to_dir    INTEGER NOT NULL,
    node      INTEGER NOT NULL,
    penalty   INTEGER NOT NULL DEFAULT -1,
    notes     TEXT,
    CONSTRAINT "link_fk" FOREIGN KEY("link") REFERENCES "Link"("link") DEFERRABLE INITIALLY DEFERRED, -- check
    CONSTRAINT "to_link_fk" FOREIGN KEY("to_link") REFERENCES "Link"("link") DEFERRABLE INITIALLY DEFERRED, -- check
    CONSTRAINT "to_node_fk" FOREIGN KEY("node") REFERENCES "Node"("node") DEFERRABLE INITIALLY DEFERRED
);
create INDEX IF NOT EXISTS idx_polaris_turns_nod ON Turn_Overrides (node);
CREATE UNIQUE INDEX IF NOT EXISTS idx_polaris_turns_link_pair ON Turn_Overrides (link, to_link, node);